Suzuki T, Sato C, Tanaka R
Department of Biochemistry, Nagoya City University Medical School, Mizuho-ku, Nagoya 467 Japan.
Neurochem Int. 1988;13(1):53-61. doi: 10.1016/0197-0186(88)90102-7.
SJ proteins termed P1, P2, P3 and P4 were found to have molecular weights very close to MAP1 or MAP2. P1 and P2 reacted with an antibody to the combined antigens, MAP1a, MAP1b and MAP1c, but neither one of the peptide maps of P1, P2, nor P3 resembled either one of the maps of MAP1a plus MAP1b, MAP1c, MAP2a or MAP2b. Thus, proteins 1 and 2 were immunologically related to, but structurally different from, MAP1 subspecies. The protein P4 reacted with an antibody to combined MAP2a and MAP2b, and a peptide map of P4 resembled those of MAP2a and MAP2b. Thus, P4 is probably identical to MAP2. P1, P2, P3 and P4 appeared to be concentrated in SJ as compared to synaptosomes or a synaptic plasma membrane fraction, although the contents of these proteins, especially P1 and P4, were small. P2 (MAP1-related protein) was phosphorylated endogenously both in the presence and in the absence of CaC1(2) plus calmodulin, while the MAP2-related protein P4 in SJ was hardly phosphorylated by the endogenous kinases.
被称为P1、P2、P3和P4的突触小体蛋白被发现其分子量与微管相关蛋白1（MAP1）或微管相关蛋白2（MAP2）非常接近。P1和P2与针对组合抗原MAP1a、MAP1b和MAP1c的抗体发生反应，但P1、P2以及P3的肽图均与MAP1a加MAP1b、MAP1c、MAP2a或MAP2b的肽图不同。因此，蛋白1和2在免疫上与MAP1亚类相关，但在结构上与之不同。蛋白P4与针对组合的MAP2a和MAP2b的抗体发生反应，且P4的肽图与MAP2a和MAP2b的肽图相似。因此，P4可能与MAP2相同。与突触小体或突触质膜组分相比，P1、P2、P3和P4似乎在突触小体中富集，尽管这些蛋白的含量，尤其是P1和P4的含量较少。P2（与MAP1相关的蛋白）在有和没有氯化钙加钙调蛋白的情况下均会发生内源性磷酸化，而突触小体中与MAP2相关的蛋白P被内源性激酶磷酸化的程度很低。
